In 2008, Pongola Game Reserve became one of the first reserves in Africa to implement a vasectomy programme to control its elephant population growth. The project was funded by the Elephant Population Management Program in an attempt to test the alternatives to culling in areas with perceived over-populations of elephant. Of the nine adult bulls, seven bulls were vasectomised, one was removed from the population, and the remaining bull was treated with gonadotrophin-releasing hormone (GNRH) suppressant to prevent them for entering musth.
WEI were invited to become involved with the post-vasectomy monitoring of the population in 2008. As the gestation period of elephant is 22 months, the first milestone to the project would be around two years after the vasectomies; this is when we would expect no further births. However, this was not the case and the population continued to grow. It is likely that the source of this problem was the inaccurate dosage of GNRH suppressant. The treated male was still seen to be entering a musth and so is likely to have continued mating but, without expensive genetic testing, it is impossible to be sure. Therefore, we still can't be certain that the vasectomies have been a success.
Although we won’t know about the efficacy of the vasectomy surgery until we source funding for the genetic testing, the main aim of our post vasectomy monitoring was to gain a better understanding of the effects of vasectomies on bull behaviour, especially the impact on dominance hierarchies, interactions between the herd and other bulls, and their ranging and habitat preferences. Early indications have suggested that the vasectomies have had no significant effect on social or sexual behaviour. Our data has also highlighted a number of younger males who are now starting to show interest in females and should be considered as candidates for vasectomies in the near future.
As the elephant population is now well above the predicted carrying capacity, the reserve still faces major decisions around its elephant management programme. The most attractive solution would be drop boundary fences with adjacent properties to increase the land area available to the elephant, therefore reducing the concentrated grazing and vegetation damage. If this is to be a viable option, it is important that neighbouring reserves are given the best possible predictions on the impact that elephants will have on their land. WEI’s research on Pongola has also involved detailed habitat assessments of elephant impact, highlighting the habitats, vegetation communities, species, and geographical areas most vulnerable to elephant impact. This data can then be extrapolated onto neighbouring properties to create a predictive map of impact over time.
The final section of our research investigates social interactions between groups on the reserve. If it is decided that the only viable option on the reserve is to remove a number of individuals, research in this area will help us to identify suitable candidates for removal to ensure the minimal disruption to the population.Selected Outputs:
- Recommendations for Elephant Management at Pongola Private Game Reserve, South Africa
- How vasectomy affects elephant behaviour in the longer term
- Sterilisation of elephants impacts on their behaviour
- The impact of male contraception on dominance hierarchy and herd association patterns of African elephants (Loxodonta africana) in a fenced game reserve